Indian airline IndiGo said it plans to start flying smaller planes to second-tier towns and cities later this year, in a shift in strategy for the carrier that has prided itself on the simplicity of running only one type of jet.

IndiGo, which has a fleet of 131 Airbus A320 aircraft, said on Tuesday it has placed a provisional order for 50 ATR 72-600 aircraft from European turboprop maker ATR, worth over $1.3 billion at list price.

IndiGo joins national carrier Air India and SpiceJet which have finalized plans under Prime Minister Narendra Modi's scheme to make it cheaper for people to fly within India. The scheme subsidizes part of the cost for airlines to fly to smaller towns.

"We should see increased business activity in small towns and cities which will increase demand for air travel in these regions," IndiGo's President Aditya Ghosh said after the company reported a 25 percent fall in quarterly net profit.

InterGlobe Aviation Ltd, owner of IndiGo, said net profit fell to 4.4 billion rupees ($68 million) in the quarter ended March 31, from 5.84 billion rupees a year ago, as fuel costs jumped 71 percent over the same period.

The company said it expects available seat kilometer, a key measure of an airline's capacity, to increase by 22 percent in the April-June quarter.

IndiGo, which has maintained its efficiency by operating only one type of aircraft, said it plans to set up a separate unit to manage the ATR fleet to reduce the complexity of flying two different types of aircraft.

Functions such as flight operations, in-flight services, route planning and revenue management will be managed by a separate team, whereas administrative functions like human resources, finance and legal would be controlled by IndiGo.

"It would avoid adding complexity to mainline operations," Ghosh said during an analyst call, adding that it would also result in synergies in corporate overheads and ground handling.

The company said it expects to have up to seven ATR aircraft by March 2018 if it reaches an agreement to buy the planes.

IndiGo also expects to add 39 new aircraft in the current fiscal year that started on April 1, of which 28 will be A320neos, taking the total to 170 A320 aircraft.

The carrier has faced operational issues with some A320neo aircraft due to problems with engines built by Pratt & Whitney, a unit of United Technologies Corp.

Ghosh said IndiGo expects Pratt & Whitney to provide a solution to one part of the problem by the fourth quarter of 2018 and the engine maker is working on a new design solution that will be retro-fitted later.

Pratt & Whitney has also carried out hardware and software changes on all of IndiGo's A320neos which should address part of the issue, he said.

IndiGo has ordered a total of 430 A320neo aircraft in the past two years, making it one of Airbus's biggest customers.